1. Field of the Invention
The present invention generally relates to a method, system and program product for attaching a title key to encrypted content for synchronized transmission to a recipient. Specifically, a title key used to encrypt content is itself encrypted, and attached to the encrypted content so that both can be synchronously transmitted to a recipient.
2. Background Art
In the transmission of digital signals, content such as video and audio data is often transmitted from a signal source to a receiver. In transmitting such content, however, the security thereof must be ensured. In general, security of the content is provided by encrypting the content with a key, and then transmitting the encrypted content to the receiver. If compliant, the receiver is able to receive and decrypt the content. In securing the content in this manner, multiple keys can be used. For example, a first content packet might be encrypted with a first key, while a second content packet might be encrypted with a second key. The use of multiple keys provides enhanced security by preventing an entire content stream from being accessed with a single key. In such a scenario, however, it is essential for synchronization between the encrypted content and the corresponding keys to be maintained. That is, the receiver must be able to match content with the correct key. If matching is not maintained, the incorrect key might be used and the content could not be decrypted.
Current technologies that utilize key-based security practices include a personal computer-based Digital Rights Management System (DRMS) and a Conditional Access System (CAS). In the case of the former, content is packaged and loaded onto a web server. The keys used to encrypt/decrypt the content are downloaded to the personal computer, but not as an integral part of the content. Rather, either at download or rendering time, the receiver must access a license server to receive permission to access the content and a description of any corresponding usage rules.
In a television-based CAS, the content and keys are prepared at a head-end server based on the appropriate subscriber information. The encrypted content and keys are delivered in a multiplexed stream as separate data entities that must be synchronized with each other through various bit flags. At rendering time, the receiver will generally use a local smart card processor to receive permission to access the content so that no direct communication with the server is required. Thus, the CAS relies on bit flags to synchronize the keys to the encrypted content. Moreover, the CAS generally utilizes alternating keys (referred to as even and odd). That is, de-scrambling the content starts with the receipt of a key pair. The first key (e.g., the even) is used for a predetermined period to decrypt the content, after time which the second key is used. Once the second key starts being used, a new key pair can be sent to the receiver. In sending separate key sets to the receiver in this manner, however, loss of synchronization between the content and the keys is risked. Moreover, both DRMS and CAS can have inherent latencies in providing random access of protected content.
In view of the foregoing, there exists a need for a method, system and program product for attaching a key to encrypted content for synchronized transmission to, or storage by, a receiver. That is, a need exists for a key used to encrypt content to be itself encrypted, and transmitted as an integral part of the content. By transmitting the encrypted key as an integral part of the encrypted content, a receiver would receive the encrypted content as well as all information necessary to decrypt the content in a single stream. Moreover, by transmitting the encrypted key and encrypted content as a single stream, compatibility and compliance with existing front-end and back-end standards would be maintained. In addition, synchronous transmission to (and storage by) a receiver fosters random access to the content.